[Beowulf] mpich program segfaults

Suvendra Nath Dutta sdutta at deas.harvard.edu
Thu Mar 4 06:26:49 EST 2004


Glen,
	I am sorry, I meant buffer-overrun instead of memory overrun. It
is of course impossible to say, but you are describing a classic
description of buffer overrun. Program seg-faulting, some where there
shouldn't be a problem. This is usually because you've over run the array
limits and are writing on the program space.
				Suvendra.

On Wed, 3 Mar 2004, Glen Kaukola wrote:

> Suvendra Nath Dutta wrote:
>
> > Glen,
> >     Does your program seg fault when compiled with debugging off or on?
>
>
> Either way.
>
> > Sometimes compilers will initialize arrays when compiling for
> > debugging, but not waste time doing that when compiled without debugging.
>
>
> The arguments being passed to the subroutine are two arrays of real
> numbers and a few integers.  Nothing being passed to the subroutine has
> been dynamically allocated.  The compiler, IBM's XLF compiler,
> initializes the array to 0.  At least I'm pretty sure it does, since I
> can print things before the subroutine call.
>
> > Also if you compile with optimization which line follows which one
> > isn't always clear.
>
>
> I don't have any optimizations turned on.
>
> > You want to make sure you aren't over-running memory.
>
>
> The machine has 2 gigs of memory, which should be plenty.  The same
> program runs on an x86 machine with 1 gig of memory just fine (I'm
> trying to get the program working on an Apple G5 by the way).
>
> > Also you want to be sure its nothing to do with MPICH. Try calling the
> > subroutine from a serial program if possible.
>
>
> I've tried telling mpirun to only use one cpu and I get the same
> results.  I've also tried running the program all by itself and it still
> crashes.  Like I said though, it runs just fine under the a debugger.
>
>
> Glen
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